The invention presented here concerns a scanning device suited for the opto-mechanical processing of a substrate covered with photo-sensitive material, using optical components supported by a mobile carriage which moves along a rectilinear guide.
The invention finds numerous applications in the area of printing, cartography, medical imaging for the generation of graphical documents, as well as for the input and analysis of such documents, including for the purpose of converting the information of these documents into a digital form.
There presently exist photocomposition devices, in which a drum covered with a photo-sensitive sheet is scanned by a narrow light bean reflected by a mirror supported by a carriage or a slide. This carriage or slide is actuated by a lead screw, which, in turn, is driven by an electric motor. The primary drawback of such a carriage positioning system is the lack of positioning precision of the carriage or slide, as a consequence of mechanical vibrations, backlash and wear.
There also exist scanning devices in which a narrow light beam explores a sheet by scanning the latter point-by-point, in a linear fashion, and transferring, as a function of the beam position, the optical information to a computer which directs the analyzing beam.
In those known machines or devices, the scanning element, consisting of said carriage or slide, is actuated by means of lead screws. The accuracy required, which is of the order of 1 micrometer, renders both the construction and the positioning control of these positioning systems complex and expensive. Furthermore, mechanical lead screws incur mechanical wear, resulting in backlash and poor carriage positioning accuracy.